Glenoid component with offset center and associated methods

ABSTRACT

A glenoid component having an offset center of articulation and associated systems and methods.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119 of U.S.Provisional Application No. 61/263,994, filed on Nov. 24, 2009, entitled“Glenoid Component with Offset Center,” which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND

Glenoid components generally include a body with two, opposing faces—afirst face designed to articulate with either a natural or a prosthetichead of a humerus, and a second face designed to be pressed against theglenoid cavity of a shoulder blade and to be immobilized therein. Thefirst face typically includes a spherical joint surface while the secondface is provided with a fin, one or more pegs, or other means foranchoring the component into the bone forming the glenoid cavity.

The two faces of glenoid components are typically designed to becentered on one and the same geometric axis, that axis corresponding tothe direction of implantation of the glenoid component into the glenoidcavity. In other words, the spherical joint surface is geometricallycentered on a point belonging to the geometric axis and the fin orcentral anchoring peg, for example, are also centered on the geometricaxis.

SUMMARY

Some embodiments relate to a glenoid component having anti-dislocationaction in a periphery of a body of the component. In some embodiments,the glenoid component has an offset center.

Some embodiments relate to a method of repairing a shoulder joint of apatient, the method including exposing a glenohumeral joint, theglenohumeral joint including a humerus and a glenoid. A glenoidcomponent is implanted into the glenoid, the glenoid component having abody and an anchor portion, the body defining an articulation surfaceand an anchor surface opposite the articulation surface. The anchorportion is centered on the body along a central axis of the glenoidcomponent, where the articulation surface is curved and has an apicalportion that is offset in a first direction from a central axis of theimplant and a raised peripheral portion offset in a second directionfrom the central axis of the implant, the second direction beingopposite the first direction. A humeral head is engaged with thearticulation surface such that the humeral head is seated against theapical portion of the articulation surface when the humeral head is in aneutral position. The humeral head is articulated against thearticulation surface from the neutral position to a modified positionsuch that the humeral head transitions from the apical portion towardthe raised peripheral portion to assess a risk of luxation between thehumeral head and the glenoid component when the humeral head is movedtoward the modified position.

Some embodiments relate to a method of replacing a glenohumeral jointincluding engaging a humeral head with an articulation surface of aglenoid component in a first, neutral position such that the humeralhead is positioned against a center of articulation that is offset froma central axis of the glenoid component. The central axis is defined atan intersection of first and second mid-planes of the glenoid componentthat are orthogonal to one another. The method also includesarticulating the humeral head to a second position such that the humeralhead is engaged with a peripheral portion of the articulation surfacethat is raised relative to the center of articulation and offset fromthe central axis in an opposite direction than the center ofarticulation such that a tension in the glenohumeral joint retaining thehumeral head against the articulation surface is increased.

Still other embodiments relate to a glenoid component including a bodyforming an articulation surface configured for engaging a humeral headand an anchor surface configured for engaging a glenoid cavity of ashoulder. The body has a first mid-plane, a second mid-plane orthogonalto the first mid-plane, and a central axis at an intersection of thefirst and second mid-planes. The articulation surface is substantiallyconcave and defines a center of articulation and a raised peripheralportion, the center of articulation being located at an apical portionof the articulation surface and offset from both the first and secondmid-planes in a first direction from the central axis. The raisedperipheral portion is offset from the first and second mid-planes in asecond direction that is opposite to the first direction. The glenoidcomponent also includes an anchor portion connected to the body andcentered on the central axis, the anchor portion being configured forbeing embedded in a boney structure of the glenoid cavity.

This summary is not meant to be limiting in nature. While multipleembodiments are disclosed herein, still other embodiments of the presentinvention will become apparent to those skilled in the art from thefollowing detailed description, which shows and describes illustrativeembodiments of the invention. Accordingly, the drawings and detaileddescription are to be regarded as illustrative in nature and notrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a glenoid component, according to someembodiments.

FIG. 2 is a first elevation view of the glenoid component of FIG. 1implanted in the glenoid cavity of a shoulder blade that is shown intransverse section, according to some embodiments.

FIG. 3 is an elevation view of the glenoid component corresponding toperspective III of FIG. 2, according to some embodiments.

FIG. 4 is an elevation view of the glenoid component corresponding toperspective IV of FIG. 2, according to some embodiments.

Various embodiments have been shown by way of example in the drawingsand are described in detail below. As stated above, the intention,however, is not to limit the invention by providing such examples.

DETAILED DESCRIPTION

Various embodiments relate to reducing a risk of premature loosening ofglenoid components from the glenoid cavity over time that is caused byrepeated eccentric loading of the glenoid component—also described as a“rocking horse” effect. Some embodiments include a glenoid componenthaving an offset center that raises an edge of the glenoid componentrelative to a remainder of the glenoid component. In some embodiments,the raised edge is selected in an area where a humeral head has anatural tendency to sub-luxate, the raised edge thereby helping tore-center the humeral head onto a center of articulation of the glenoidcomponent.

FIG. 1 is a perspective view of a glenoid component 10 and FIG. 2 is aview of the glenoid component 10 implanted in a glenoid G of a patient,according to some embodiments. As shown in FIGS. 1 and 2, the glenoidcomponent 10 includes a body 12 and an anchor portion 14. FIG. 3 is anelevation view of the glenoid component 10 from perspective III of FIG.2, according to some embodiments. As shown in FIG. 3, the body 12 has anupper portion 22 and a lower portion 24. As shown in FIGS. 1 and 2, thebody 12 also includes a humeral side 26, a glenoid side 28, an anteriorside 30, and a posterior side 32. The body 12 is optionally multiplepieces or a single, unitary piece, as desired. The body 12 is optionallyformed of materials having rigidity and mechanical strength suitable forarticulating with a natural or artificial humeral head and for beingsecured to the glenoid cavity G of a scapula S (FIG. 2).

As shown in FIG. 3, the body 12 defines an antero-posterior mid-plane Xbetween the upper and lower portions 22, 24 and a vertical mid-plane Ybetween the first and second sides 30, 32, the mid-planes X, Yintersecting to form a central axis Z, also described as a geometricaxis of the component 10 or implant axis of the component 10. The body12 defines a first surface 42 at the humeral side 26 and a secondsurface 44 at the glenoid side 28 of the body 12, as well as an outersurface 46 extending about the body 12.

As shown, the first surface 42, also described as an articular surface,is generally curved overall and defines a center of articulation 50, aswell as a periphery 52, also described as a peripheral portion. In someembodiments, the first surface 42 is sized, shaped, and/or otherwiseconfigured to be articulated with a complementary surface of a naturalor artificial humeral head (not shown). In general terms, the firstsurface 42 is substantially spherical and defines a geometric center Oshown in FIG. 2. As shown in FIGS. 1-4, the first surface 42 optionallyoccupies most, or substantially all of the humeral side 26 of the body12.

As shown in FIGS. 1 and 2, the first surface 42 is substantially concaveand the center of articulation 50 corresponds to an apical portion ofthe concavity of the first surface 42. In other embodiments, the firstsurface 42 is substantially convex and the center of articulation 50corresponds to an apical portion of the convexity of the first surface42. As shown in FIGS. 1 and 3, the center of articulation 50 is offsetfrom the axis Z such that the center of articulation 50 is notequidistant from the periphery 52 along the direction of eithermid-plane X, Y. In some embodiments, the center of articulation 50 isoffset from the antero-posterior mid-plane X toward the lower portion 24and from the vertical mid-plane Y toward the anterior side 30 of thecomponent 10.

As described in greater detail, by offsetting the center of articulation50 from the central axis Z, the component 10 helps compensate for“rocking,” or repeated, eccentric forces that can otherwise dislocatethe component 10 from the glenoid G over time. Although FIG. 3 depictsthe center of articulation 50 offset toward the anterior side 30 and thelower portion 24, the center of articulation 50 is optionally offsetfrom the axis Z toward other portions of the component 10 (e.g., towardthe upper portion 22 and posterior side 32).

As shown in FIG. 2, the second surface 44 of the body 12, also describedas an anchoring or bearing surface, is also generally curved overall. Insome embodiments, the second surface 44 is sized, shaped, and/orotherwise configured to be secured to the glenoid cavity G as shown inFIG. 2. For example, the second surface 44 is optionally substantiallyconvex and configured to press against a surface of the glenoid cavity Gthat faces toward the humerus, where the second surface 44 defines acentral region 58 at an apical portion of its convexity. Although thesecond surface 44 is shown as being substantially convex, in otherembodiments the second surface 44 is substantially planar or concave,for example.

As shown in FIG. 3, according to some embodiments, a transverseprojection of the body 12 relative to the axis Z is substantiallysymmetrical about the mid-planes X, Y, where the upper and lowerportions 22, 24 of the body 12 include semi-circular portions P1, P2with respective radii of curvature R₁, R₂, each of which have origins onthe mid-plane Y. As shown, in transverse projection, the outer profileof the first surface 42 is in the overall shape of a pear and symmetricwith respect to the mid-plane Y. In some embodiments, the overall, pearshape of the component 10 is substantially similar to an anatomicalshape, or contour of an unimpaired glenoid cavity G such that the secondsurface 44 of the body 12 is configured to be secured to the glenoidcavity G with the body 12 generally fitting the outer contour of thecavity G.

As shown, the center of articulation 50 is offset with respect to theaxis Z, anatomically forward (anterior) and downward (inferior) on theglenoid component 10 as configured in the glenoid cavity G followingimplantation. In particular, according to some embodiments, uponimplantation of the component 10, the mid-plane X runs in asubstantially antero-posterior anatomical direction and the mid-lane Yruns in a substantially vertical, or infero-superior anatomicaldirection, while the axis Z projects into the glenoid cavity G andscapula S in the direction of implantation of the component 10 in theglenoid cavity G. In other words, the center of articulation 50 belongsto an infero-anterior quadrant of the body 12. In turn, asuperio-posterior portion of the first surface 42 is generally raised,or elevated, in comparison with a remainder of the body 12 in thedirection of the axis Z. In other words, the periphery 52 is raised inthe upper portion 22 of the body 12 toward its posterior side 32. Thisraised portion of the periphery 52 reduces risk of sub-luxation betweenthe glenoid component 10 and the humeral head (natural or prosthetic)when the humeral head is articulated toward the raised portion of theperiphery 52.

In some embodiments, the center of articulation 50 is offset by adistance dY between the center of articulation 50 and the mid-plane Y ofat least 5%, from about 5% to about 10%, of at least 10%, or at least20%, for example, of a maximum orthogonal distance DY between themid-plane Y and the transverse projection of the body 12 relative to theaxis Z. In some embodiments, the center of articulation 50 is offset bya distance dX between the center of articulation 50 and the mid-plane Xof at least 5%, from about 5% to about 10%, of at least 10%, or at least20%, for example, of a maximum orthogonal distance DX between themid-plane X and the transverse projection of the body 12 relative to theaxis Z.

As shown in FIGS. 1, 2, and 4, the anchor portion 14 is shaped as a fin,or keel, where the anchor portion 14 is substantially plate-shaped witha mid-plane P (FIG. 4) that extends transversely to the second surface44 of the body 12. In some embodiments, the anchor portion 14 is sized,shaped, and/or otherwise configured to be embedded and immobilized inthe glenoid cavity G and optionally includes features for promoting bonegrowth, or secondary attachment. As shown in FIG. 2, the anchor portion14 defines a first end face 60 and a second end face 62 through whichthe mid-plane P passes (FIG. 4), as well as a first primary face 64 anda second primary face 66 (FIG. 4) positioned opposite to the firstprimary face 64. The anchor portion 14 also includes a through hole 70,as well as grooves 72 that optionally serve to form spaces forencouraging secondary fixation via bone ingrowth. In other embodiments,a primary peg (not shown) is used for the anchor portion 14, where theprimary peg extends substantially coaxially with the axis Z.

As shown, the anchor portion 14 is centered on the axis Z of themid-planes X, Y of the body 12, where the anchor portion 14 is implantedin the glenoid cavity in the direction of the axis Z. In someembodiments, the axis Z is central to the anchor portion 14, extendingalong the mid-plane P, and running substantially equidistant from thefirst and second end faces 60, 62, as well as the first and secondprimary faces 64, 66 of the anchor portion 14.

Some methods of implanting the glenoid component 10 and centering ahumeral head on the glenoid component 10 include a surgeon exposing theglenohumeral joint, dislocating the humerus from the glenohumeral joint,forming or replacing the natural humeral head, forming the glenoidcavity G, implanting the glenoid component 10 into the glenoid cavity Galong the axis Z, and articulating the humeral head with the glenoidcomponent 10. In some embodiments, the glenohumeral joint is exposedusing known techniques and the humerus is similarly dislocated from theglenoid G. The glenoid G is optionally formed or otherwise configured toreceive the glenoid component 10.

In some embodiments, the glenoid component 10 is implanted into theglenoid G along the central axis Z such that the antero-posteriormid-plane X is oriented generally antero-posteriorly relative to thepatient and the vertical mid-plane Y is oriented generallyinfero-superiorly relative to the patient. In some embodiments, thecenter of articulation 50 is thus offset in an inferior and anteriordirection relative to the central axis Z following implantation in theglenoid G. As part of implantation, the anchor portion 14 is optionallyembedded into a cavity or pocket formed into the bony structure of theglenoid G and the second surface 44 is received against bony structuresof the glenoid G in a complementary fit.

In some embodiments, the humeral head is prepared (e.g., via formingprocedure) to better articulate with the glenoid component 10 and/or aportion of the humerus (e.g., the proximal humeral head) is removed andreplaced with an artificial humeral head. Regardless, in someembodiments, the humeral head is engaged with the first surface 42 suchthat the humeral head is seated against the apical portion of thearticulation surface when the humeral head is in a neutral position,where the “neutral position” is meant to correspond to a position wherethe humerus is hanging freely at the patient's side.

In order to evaluate performance of the glenohumeral joint, the humeralhead is articulated against the first surface 42 from the neutralposition to a modified position (e.g., including flexion, extension,abduction, adduction, lateral rotation, and/or medial rotation) suchthat the humeral head transitions from the apical portion at the centerof articulation 50 toward the raised part of the periphery 52 to assessa risk of luxation between the humeral head and the glenoid component 10when the humeral head is moved toward the modified position.

If the assessment is unfavorable, the surgeon optionally replaces theglenoid component 10 with another glenoid component having a differentoffset between the center of articulation 50 and the central axis Z, adifferent amount of curvature for the first surface 42, and/or adifferently sized glenoid component, for example. If the assessment isfavorable, the surgeon closes the glenohumeral joint and evaluates thetension in the joint through a variety of positions, including at theneutral and modified positions. Generally, the modified position resultsin the humeral head being moved outwardly, away from the glenoid G whichtightens the joint and avoids dislocation of the humeral head from thefirst surface 42, thereby reducing dislocation risk. In other words, thehumeral head is engaged with a peripheral portion of the first surface42 that is raised relative to the center of articulation 50 and offsetfrom the central axis Z in an opposite direction than the center ofarticulation 50 such that the tension in the glenohumeral jointretaining the humeral head against the articulation surface 42 isincreased.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of invention. Forexample, various body shapes are contemplated, including substantiallycircular or irregular shapes, as well as various anchoring portions,including pegs, screws, and/or others. As used herein, the terms“upper,” “lower,” “front,” “back,” “left,” “right,” “top,” “bottom,” andthe like are relative positional terms, used for description purposes,and are not to be taken in an overly limiting sense. While theembodiments described above refer to particular features, the scope ofinvention also includes embodiments having different combinations offeatures and embodiments that do not include all of the above describedfeatures.

1. A method of repairing a shoulder joint of a patient, the methodincluding: exposing a glenohumeral joint, the glenohumeral jointincluding a humerus and a glenoid; implanting a glenoid component intothe glenoid, the glenoid component having a body and an anchor portion,the body defining an articulation surface and an anchor surface oppositethe articulation surface and the anchor portion being centered on thebody along a central axis of the glenoid component, where thearticulation surface is curved and has an apical portion that is offsetin a first direction from a central axis of the implant and a raisedperipheral portion offset in a second direction from the central axis ofthe implant, the second direction being opposite the first direction;engaging a humeral head with the articulation surface such that thehumeral head is seated against the apical portion of the articulationsurface when the humeral head is in a neutral position; and articulatingthe humeral head against the articulation surface from the neutralposition to a modified position such that the humeral head transitionsfrom the apical portion toward the raised peripheral portion to assess arisk of luxation between the humeral head and the glenoid component whenthe humeral head is moved toward the modified position.
 2. The method ofclaim 1, wherein the articulation surface is substantially concave suchthat the humeral head is seated against the apical portion of theconcavity of the articulation surface when the humeral head is in aneutral position.
 3. The method of claim 1, wherein the apical portionis offset in a lower, anterior direction relative to the central axis ofthe glenoid component such that the humeral head is seated against alower, anterior portion of the articulation surface when the humeralhead is in a neutral position.
 4. The method of claim 1, furthercomprising forming the humeral head from a natural head of a humerus. 5.The method of claim 1, further comprising forming the humeral head byreplacing a natural humeral head with a prosthetic humeral head.
 6. Themethod of claim 1, wherein the anchor portion includes a keel centeredon the central axis and implanting the glenoid component into theglenoid includes embedding the keel into the glenoid in a direction ofthe central axis.
 7. The method of claim 1, wherein the anchor portionincludes a peg centered on the central axis and implanting the glenoidcomponent into the glenoid includes embedding the peg into the glenoidin a direction of the central axis.
 8. A method of replacing aglenohumeral joint including engaging a humeral head with anarticulation surface of a glenoid component in a first, neutral positionsuch that the humeral head is positioned against a center ofarticulation that is offset from a central axis of the glenoidcomponent, the central axis being defined at an intersection of firstand second mid-planes of the glenoid component that are orthogonal toone another and articulating the humeral head to a second position suchthat the humeral head is engaged with a peripheral portion of thearticulation surface that is raised relative to the center ofarticulation and offset from the central axis in an opposite directionthan the center of articulation such that a tension in the glenohumeraljoint retaining the humeral head against the articulation surface isincreased.
 9. The method of claim 8, wherein the glenoid componentdefines a transverse perimeter relative to the central axis that issubstantially complementary in shape to a natural glenoid cavity of theglenohumeral joint.
 10. The method of claim 8, further comprisingimplanting the glenoid component into a glenoid cavity of theglenohumeral joint in a direction of the central axis.
 11. The method ofclaim 8, further comprising forming the humeral head by replacing anatural humeral head with a prosthetic humeral head.
 12. The method ofclaim 8, wherein the center of articulation is offset in an inferior andanterior position relative to the central axis and the peripheralportion is raised in a superior and posterior position relative to thecentral axis.
 13. The method of claim 8, wherein articulating thehumeral head to the second position includes at least one of flexion,extension, abduction, adduction, lateral rotation, and medial rotationof a humerus corresponding to the humeral head.
 14. A glenoid componentcomprising: a body forming an articulation surface configured forengaging a humeral head and an anchor surface configured for engaging aglenoid cavity of a shoulder, the body having a first mid-plane, asecond mid-plane orthogonal to the first mid-plane, and a central axisat an intersection of the first and second mid-planes, the articulationsurface being substantially concave and defining a center ofarticulation and a raised peripheral portion, the center of articulationbeing located at an apical portion of the articulation surface andoffset from both the first and second mid-planes in a first directionfrom the central axis and the raised peripheral portion being offsetfrom the first and second mid-planes in a second direction that isopposite to the first direction; and an anchor portion connected to thebody and centered on the central axis, the anchor portion beingconfigured for being embedded in a boney structure of the glenoidcavity.
 15. The glenoid component of claim 14, wherein the anchorportion includes a keel structure centered on the first mid-plane andcentral axis.
 16. The glenoid component of claim 14, wherein the centerof articulation corresponds to an inferiorly and anteriorly offsetposition on the articulation surface.